Pregnancy is a key opportunity to affect the epidemiology and to enhance reduction of women's tobacco and problem alcohol use. The opportunities to provide pregnant women with tobacco and alcohol cessation resources appear to be strongest when integrated into community-based health services, with attention to generating support in mothers' networks of family and friends. Ecological models of maternal substance use to date have tended to examine a limited set of social processes or neighborhood structural characteristics but not both, to focus on smoking only, and to focus on infant outcomes, while studies of neighborhood effects on birth outcomes may fail to include maternal substance use. The limited development of contextual theory focused on maternal substance use as an outcome is part of the problem. The goal of the proposed research is to investigate the role of neighborhood structural aspects and social processes in association with maternal alcohol and tobacco use in the perinatal and early childhood parenting periods. Specifically, we will investigate the relationship between individual characteristics of mothers (in a nationally representative dataset) and the social ecology of neighborhoods as predictors of maternal alcohol and tobacco use patterns over time. The availability of a rich set of neighborhood social process variables in the Birth Cohort of the Early Childhood Longitudinal Survey dataset will be augmented by constructs of neighborhood socioeconomic status and material deprivation based on data from the 2000 Census, and neighborhood smoking prevalence estimates from the Current Population Survey-Tobacco Use Supplement 2000. Our proposed research will examine how neighborhood structural characteristics and social processes relate to each other and to individual characteristics that are the proximate determinants of maternal substance use from preconception through the early childhood parenting period. Diverging from most research to date, we will apply latent class analysis and growth mixture modeling to characterize profiles of mothers according to both their alcohol and tobacco use and individual trajectories of use over time. Individual and neighborhood measures will be examined for direct effects associated with these patterns and trajectories. Subsequently, we will apply latent variable pathway analyses to assess potential mediation of neighborhood latent variables by individual characteristics, and we will analyze whether results of pathway analyses apply to different subgroups of our sample (moderation analyses). The results will be applied toward further research in three directions: policy and interventions for mothers, the study of child health outcomes, and enhanced research in social processes, structural effects, and policy inputs during a critical period for women's and children's health.